Electromagnetic micromotor for an electronic watch

ABSTRACT

AN ELECTROMAGNETIC MICROMOTOR FOR AN ELECTRONIC WATCH, VIBRATING AT AN ACOUSTICAL FREQUENCY AND ADAPTED TO BE CONTROLLED BY A VERY STABLE OSCILLATOR. THE MICROMOTOR COMPRISES AN ELASTIC PORTION CONNECTED WITH AN OSCILLATING MASS PORTION CARRYING AN IMPULSE PAWL COOPERATING WITH A RATCHET WHEEL DRIVING THE GEAR-TRAIN OF THE WATCH, A STOP PAWL, COOPERATING WITH THE SAME RATCHET WHEEL, BEING MOUNTED ON THE FRAME OF THE MICROMOTOR. THE RATCHET WHEEL AND THE SAID PAWLS ARE SITUATED IN A PLANE PERPENDICULAR TO THE PLANE OF THE WATCH MOVEMENT AND AN INCLINED MIRROR RENDERS POSSIBLE THE OBSERVATION OF THE MOTION OF THE SAID RATCHET WHEEL AND OF THE SAID PAWLS THROUGH AN OPTICAL AXIS PERPENDICULAR TO THE PLANE OF THE WATCH MOVEMENT.

A. CACHIN ELECTROMAGNETIC MICROMOTOR FOR AN ELECTRONIC WATCH Filed May 28, 1970 INVENTOR UnitedStates Patent ()1 fice 3,608,302 Patented Sept. 28., 1971 US. Cl. 58-23 3 Claims ABSTRACT OF THE DISCLOSURE An electromagnetic micromotor for an electronic watch, vibrating at an acoustical frequency and adapted to be controlled by a very stable oscillator. The micromotor comprises an elastic portion connected with an oscillating mass portion carrying an impulse pawl cooperating with a ratchet wheel driving the gear-train of the watch, a stop pawl, cooperating with the same ratchet wheel, being mounted on the frame of the micromotor. The ratchet wheel and the said pawls are situated in a plane perpendicular to the plane of the watch movement and an inclined mirror renders possible the observation of the motion of the said ratchet wheel and of the said pawls through an optical axis perpendicular to the plane of the watch movement.

The present invention relates to an electromagnetic micromotor for an electronic watch, vibrating at an acoustical frequency and adapted to 'be controlled by a very stable oscillator, comprising an elastic portion connected with an oscillating mass portion carrying an impulse pawl cooperating with a ratchet wheel driving the gear-train of the watch, a stop pawl, cooperating with the same ratchet wheel, being mounted on the frame of the micromotor. This micromotor is broadly characterized in that the ratchet wheel and the saidpawls are situated in a plane perpendicular to the plane of the Watch movement and that an inclined mirror renders possible the observation of the motion of the said ratchet wheel and of the said pawls through an optical axis at least approximately perpendicular to the plane of the watch movement.

The accompanying drawing illustrates, by way of example, an embodiment of the invention.

The single figure is a perspective view of said embodiment.

The micromotor illustrated in the drawing includes a U-shaped frame 1 the base 1a of which is rather massive, whereas its legs 1b and 1c are thinner and present a certain elasticity in a plane parallel to the pillar-plate 25. The elastic portion of the micromotor consists of a plane torsion blade 2, perpendicular to the plane of the watch, the longitudinal axis of said blade being parallel to the plane of the watch. The torsion blade 2 is embedded at its both ends in the legs 1b and 1c of the frame 1 and carries in the middle thereof the mass portion, which is formed by a rigid bar 3, distributed on both sides of the torsion blade 2. At the ends of the bar 3 are respectively fixed a coil 4 and a counterweight 5 in such a manner that a static equilibrium is obtained about the axis of the torsion blade 2. The coil 4 is electromagnetically connected with a stationary magnetic circuit consisting of a pair of permanent magnets 6 and two pairs of polar pieces 7, 8. This electromagnetic device, which does not belong to the invention, is controlled by a very stable oscillator, for instance a quartz oscillator.

The legs 1b and 1c of the frame 1, in which are embedded the ends of the torsion blade 2, quarantee a strong rigidity in the direction of rotation of the mass or bar 3', but allow a longitudinal displacement of the embedding points, which displacement is caused by the shortening of the torsion blade 2 during its oscillation.

The bar 3 carries an impulse pawl 9' cooperating with a ratchet wheel 10 the shaft 11 of which is pivoted between two small plates 12; the shaft 11 carries a worm 13 which is in mesh with the first wheel 14 of the gear-train of the watch. The reference numeral 15 denotes the trainbridge and 25 the pillar-plate of the watch, the frame 1 being mounted on said pillar-plate 25. Thus, the micro motor forms a sub-assembly of the-watch, situated at least partially above the gear-train of the watch.

The leg 1b of the frame 1 has an inner flange 16 above which is placed a plate 17 made integral with a blade 18 which is fixed to the base 1a of the frame 1. The blade 18 is resilient in two planes which are respectively parallel and perpendicular to the pillar-plate 25 and tends, on the one hand, to lift the plate 17 away from the flange 16, but this is prevented by a screw 19 screwed in the flange 16 and bearing on the upper face of the plate 17, said screw 19 thus maintaining the parts 16 and 17 spaced from each other. On the other hand, an eccentric 20, driven into the flange 16 and whose head is accommodated within an elongated opening 21 of the plate 17, enables the user to slightly displace the plate 17 in a direction transverse to the bar 3. An extension 22 of the plate 17 carries a stop pawl 23 cooperating with the ratchet wheel 10. By turning the screw 19, it is possible to adjust the phase of the stop pawl 23, whereas, by means of the eccentric 20, it is possible to adjust the pressure of this pawl 23.

A mirror 24, consisting here of a prism, is arranged in the vicinity of the ratchet wheel 10 and its active surface is inclined at 45 with respect to the plane of the watch movement. By means of this mirror 24, it is possible to observe the motion of the ratchet wheel 10 and of the pawls 9 and 23, which are situated in a plane perpendicular to the plane of the watch movement, through an optical axis perpendicular to the plane of the watch movement. The provision of the mirror 24 facilitates the adjusting of the the stop pawl 23 and permits an easy checking of the operation.

The operation of the micromotor as illustrated is easily understood with the help of the foregoing description. When the stable oscillator controlling the electromagnetic device 4, 6, 7, 8 operates, the bar 3 begins to oscillate at an acoustical frequency and the torsion blade 2 acts as a drawback elastic member. The impulse pawl 9, fixed to the bar 3, advances step by step the ratchet wheel 10 and the latter, through the intermediary of the worm 13, drives the wheel 14 of the gear-train of the watch.

What is claimed is:

1. An electromagnetic micromotor for an electronic watch adapted to be controlled by a very stable oscillator and having a watch movement including a gear train, comprising a frame, a ratchet wheel mounted on said frame in driving relation with the watch movements gear train, an elastic portion mounted on said frame and connected with an oscillatable mass carrying an impulse pawl cooperating with said ratchet wheel, a stop pawl mounted on said frame and engageable with said ratchet wheel, an inclined mirror mounted on said frame, said ratchet wheel and said pawls being situated in a plane perpendicular to the plane of the watch movement, said inclined mirror enabling the observation of the motion of said ratchet wheel and said pawls through an optical axis at least approximately perpendicular to the plane of the watch movement.

2. A micromotor according to claim 1, wherein the said mirror consists of a prism.

active surface of the said mirror is inclined at 45 with respect to the plane of the watch movement.

References Cited UNITED STATES PATENTS 2,726,571 12/1955 Chang 5850X 3,176,171 3/1965 Baumgartner 310--38 3,540,205 11/1970 Hetzel 58230 RICHARD B. WILKINSON, Primary Examiner E. C. SIMMONS, Assistant Examiner US. Cl. X.R.

3. A micromotor according to claim 1, wherein the 15 310-43 

